Resting metabolic rate (RMR) and the thermic effect of feeding (TEF) two meals of differing energy densities were measured in 8 healthy elderly men aged 63–74 years. Similar measurements were made on 8 healthy young men aged 22–28 years. TEF was related to the meal size in both groups. Metabolic rate increased by 20.7 and 27.9% in the elderly group (EG) and 25.8 and 37.7% in the control group (CG) in response to the 2.0- and 4.0-MJ meals, respectively. Although the EG were fatter than the CG, they consumed a smaller daily food intake: we suggest that the decline in RMR and TEF as indicated by the study would explain this para